Electric cut-out



maar n., 24, um v2,118,545

UNITED STATES PATENT OFFICE ELECTRIC CUT-OUT Edgar A. Harty Marblehead, Mal., assigner to NGenenlYoEleci-lc Company. a corporation of Application November 17, 1937, Serial No. 174,920

Claiml. (Cl. 20o-118) My invention relates to electric cut-outs for leakage current to ilow which, in the course of series circuits, and more particularly to oxide iiim time, deteriorates the oxide coating and causes a cut-outs, the present application being a contlnubreakdown thereof below the desired voltage. ation in part of my application s N, 126,031, med I have discovered that when in the production 5 February 16, 1937 of cut-outs, copper is used which bears a small 5 one object of my invention is to provide an percentage of another metal, such as silver for oxide illm cut-out in which the leakage current example, the resistance to current flow in both diis substantially eliminated rections, that is, in the direction of low resistance For a better understanding of my invention, as well as in the direction of high resistance oi' the together with other and further objects thereof, respective Oxide coatings iS materially increased 10 reference is had to the following description, taken and e Very D001' rectiiying ratio is Obtained. I in connection with the accompanying drawing, have found that this eUeCt becomes noticeable and its scope will be pointed out in the appended With copper containing mere traces 0f silver. Satclaims. isfactoryresults are obtained, for example, with l5 1n the production of metal oxide cnt outs, it is copper bearing silver in quantities .of the order of l5 the preferred practice to place small discs of 8 Ounces Der t0n 0f copper The Silver. 0i.' ceurse. metal, such as copper, for example, into an oxidlzneed not necessarily be contained in the copper ing atmosphere, and thereby form a coating of in itS Oriinal State, but may be valioved therewith cuprous and cupric oxides on the surface of the at any Stege 0f the manufacturing Process, before metal. One such process is disclosed in my U. S. the diScS are oxidized fOr the purpose of convert- 20 Patent No. 1,982,384, issued November 27, 1934. ing them intO cut-Outs. By this process a permanent lm of oxide is In the ecccmpenying drawing. Fig. 1, I have formed .on the copper disc, and when this digo illustrated a cut-out assembled in its protective is placed between two contacts, it provides a rejacket and in Operating POSitiOn between the sistance to current flow up to predetermined poprongs. 0r terminals, 0f a Series circuit Socket: 25 tentia1s- When suon predetermined potentials in Pig. 2, I have illustrated a cross-section of the are exceeded, the lresistance of this lm breaks cnt-Out 0f Fig. 1: and in Fig. 3, I have indicated down and current i5 permitted to ow, the relative resistance t0 Current 110W 0f Clit-Out! some difnculty has been experienced with these made with pure copper. and with copper bearing cut-outs due to breakdowns occurring below the e Small quantity 0f Silver- 30 rated voltage within a short time after the cut- Referring to this 'drawing in detail, Fig. l illusout ls placedin service. These breakdowns occur trates the prongs 5 and 6 of a series circuit socket at voltages below the rated voltage, although tests between which the assembled cut-out 1 provides indicated suicient strength of insulation when a bar to current flow until a certain voltage is exthe cut-out was first put into service. Investigaceeded- In Fig. 2, the ent-Out l is Shown in cross- 35 tions have shown that considerable leakage cur- Section and iS ShOWn t0 cOInDliSe a metal capsule rent flows through the cut-outs when they are I, a cover 9 insulated therefrom by a suitable inused on alternating current circuits. This current sul a.tion Iii placed between the edge of the cover 8 causes a rise in temperature in the cut-out and, and the wall of the capsule 8, the edge oi' the 40 consequently, a deterioration of the cut-out. The capsule being turned over to grip the cover. Con- 4o Drebable cause 0f this leakage current iS the tacting the inner surface of the capsule and cover nnidirectiOnal characteristic 0f copper Oxide is a copper disc Il, the surfaces of which are cov- Which is present in oxide films, treated as set ered with an oxide mm; forth in the above described patent, for the pur- In 3, I have illustrated a graph showing pose of limiting their breakdown strength to a the mpason between current now through 45 predetermined value. Theoretically, this unipure copper discs, covered with asingle nlm of directional characteristic should have no eect o oxide, and through oxidized discs made of silver upon the cut-out as described for the reason that b n o L1 n i tm a h l dic t each disc is provided with an oxide coating on :la ng c per' il? di nti s p n a es both sides, thereby placing two oxide coatings in t e current ow 1n e rec on o ow resistance' "'50 series with the current circuit in such manner in discs 0f pure copper at three Volts direct cui" that irrespective of the direction of the current rent? the Oxide Coating being heat-treated and ilow a high resistance will be interposed in the quenched at the temperatures indicated. The circuit. Actually, however, slight inequalities of range of quenching temperatures lndicatedinthe two opposing oxide coatings permit a small cludes those that are necessary to obtain the most 55 commonly :used breakdown voltages on cut-out discs having two opposed oxide lms on opposite sides oi the disc. Line I3 indicates the current ilow in the low resistance direction of the oxide when copper, having mere traces of silver therein the actual quantity being unmeasurable, and line I I indicates current flow when copper having a silver content of the order of 8 ounces per ton is used. The relation between these three curves indicates that the oxide lm loses some of its rectifying characteristics when a mere trace of silver appears in the copper and loses substantially all of this characteristic when a measurable quantity such as 8 ounces per ton, for example, is used. When two such films are opposed to each other, there is substantially no leakage current through the disc. The resistance of the disc subsequently to the breaking-down of the oxide is not materially affected by the presence of the silver in the disc.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A cut-out for electric circuits comprising an oxidized disc of copper having alloyed therewith a second metal which substantially eliminates the rectifying ratio o the oxide on said disc.

2. A cut-out for electric circuits comprising an oxidized disc of silver bearing copper.

3. A cut-out for electric circuits comprising an oxidized disc of copper, said copper bearing silver in suflicient quantity to substantially eliminate the rectifying characteristic of said disc.

4. A cut-out for electric circuits comprising an oxidized disc of copper, said copper bearing a quantity of silver of the order of 8 ounces per ton.

5. A cut-out for electric circuits comprising an oxidized copper disc, said copper having alloyed therewith silver of a quantity ranging from a mere trace up to 8 ounces per ton.

EDGAR A. HARTY. 

